JP2006283650A - Fuel injection quantity control device and fuel injection quantity control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for an internal combustion engine capable of effectively preventing deterioration of exhaust emission while securing good startability at a time of start of the internal combustion engine. <P>SOLUTION: This device is provided with a combustion existence determination means determining whether injected fuel normally burns or not, a residual fuel quantity estimation means estimating residual fuel quantity remaining in a cylinder without burning out of fuel injection quantity injected in the cylinder for the cylinder in which the combustion existence determination means determines that fuel normally burns, and a fuel injection quantity correction means correcting fuel injection quantity of next injection based on residual fuel quantity estimated by the residual fuel quantity estimation means for the cylinder in which the combustion existence determination means does nit determine that fuel normally burns. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine (engine), and particularly corrects the fuel injection amount at the start of the internal combustion engine in order to improve the startability at the start of the internal combustion engine and prevent emission deterioration. The present invention relates to a fuel injection control device.

2. Description of the Related Art Conventionally, in a fuel injection amount control device that controls the amount of fuel injected from an injector that is injected into an engine, the engine can be operated with an air-fuel ratio approaching a lean limit, and the amount of NOx emissions is reduced. The engine is provided with a combustion monitor sensor for detecting the combustion state in the combustion chamber, and a determination value is calculated by inputting a combustion state detection signal from the combustion monitor sensor, and the injector is detected according to the calculated determination value. A technique for providing a control means for correcting and controlling the fuel injection amount is known (for example, see Patent Document 1).
JP 07-42592 A

  In general, when starting the engine, together with cranking by the starter, fuel is injected into all cylinders without considering the synchronization with the crank angle, and after the intake stroke is executed once for all the cylinders In synchronism with the crank angle, fuel is injected into each of the plurality of cylinders in a predetermined order.

  By the way, at the time of starting the engine, particularly when the temperature is extremely low or when the fuel is inferior, the injected fuel may not burn normally in the cylinder. In such a case, a part of the injected fuel is blown through and discharged in the subsequent exhaust stroke, but the remaining part remains in the cylinder as residual fuel.

  However, conventionally, even when the injected fuel does not burn normally in the cylinder, the next fuel injection amount for the cylinder is determined as usual without considering the residual fuel as described above. Due to the fuel (and its accumulation), the fuel may become over-rich, and as a result, the startability of the internal combustion engine and the exhaust emission may be deteriorated.

  The present invention has been made in view of the above points, and provides a fuel injection control device for an internal combustion engine that can effectively prevent deterioration of exhaust emission while ensuring excellent startability when the internal combustion engine is started. For the purpose.

In order to achieve the above object, according to the present invention, combustion presence / absence determining means for determining whether or not the injected fuel burned normally,
A residual fuel amount estimating means for estimating a residual fuel amount remaining in the cylinder without burning, out of the fuel injection amount injected into the cylinder, with respect to a cylinder in which fuel is not normally determined by the combustion presence / absence determining means;
Fuel injection amount correction means for correcting the next fuel injection amount for the cylinder that is not determined to be normally burned by the combustion presence / absence determination means based on the residual fuel amount estimated by the residual fuel amount estimation means. A fuel injection amount control device is provided.

In the present invention, when the internal combustion engine is started, the fuel injection amount control device stores the injected fuel amount, and measures the rate of increase of the engine speed NE and / or the predetermined crank time immediately after ignition of the cylinder in which the fuel is injected. Further comprising means,
The combustion presence / absence determining means may determine whether or not the injected fuel has burned normally based on the rate of increase and / or a predetermined crank time. The residual fuel amount estimation means may comprise blow-by fuel amount estimation means for estimating the amount of fuel blown out from the cylinder in the exhaust stroke, and estimate the residual fuel amount from the blow-through fuel amount and the fuel injection amount. . Further, the blow-by fuel amount estimating means may estimate a blow-by fuel amount that changes according to the engine speed NE. The blow-by fuel amount estimation means may estimate the blow-by fuel amount based on a predetermined map using at least the engine speed NE as a parameter. Further, the combustion presence / absence determining means, when cranking by the starter, when the increase rate of the measured engine speed NE is higher than a predetermined reference as compared with a predetermined threshold value of the engine speed NE by cranking set in advance. It may be determined that the fuel has burned normally. In addition, after the cranking by the starter, the combustion presence / absence determining means compares the predetermined crank time immediately before ignition with the crank time immediately after ignition, and if the crank time immediately after ignition is shorter, the fuel is normal. It may be determined to have burned. The predetermined threshold value may correspond to an increase rate of the engine speed NE for only cranking by a starter. The predetermined threshold value may be corrected according to the engine water temperature and / or the state of a battery serving as a power source for the starter.

Moreover, according to the present invention, the step of determining whether or not the injected fuel has burned normally;
Estimating a residual fuel amount remaining in the cylinder without burning among the fuel injection amount injected into the cylinder for a cylinder that is not determined to be normally burned by the combustion presence / absence determining means;
Correcting the next fuel injection amount for the cylinder, which is not determined to be normally burned by the combustion presence / absence determining means, based on the residual fuel amount estimated by the residual fuel amount estimating means. A fuel injection amount control method is provided.

  As described above, according to the present invention, it is possible to obtain a fuel injection control device for an internal combustion engine that can effectively prevent deterioration of exhaust emission while ensuring excellent startability when starting the internal combustion engine.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 shows a system configuration diagram of an embodiment of an internal combustion engine 10 to which a fuel injection control device of the present invention is applied. FIG. 2 is a view showing an embodiment of the crank angle sensor plate 24.

  The internal combustion engine 10 is controlled by an electronic control unit 12 (hereinafter referred to as an engine ECU 12). The engine ECU 12 is configured by a microcomputer and includes, for example, a ROM for storing a control program, a readable / writable RAM for storing calculation results, a timer, a counter, an input interface, an output interface, and the like.

  The internal combustion engine 10 includes a cylinder block 14. A water jacket 16 is formed in the wall of the cylinder block 14. A piston 18 and a connecting rod 20 are housed inside the cylinder block 14. A crankshaft 22 is connected to the connecting rod 20.

  The internal combustion engine 10 is a 6-cylinder internal combustion engine. The six cylinders are classified into three groups based on the movement phase of the piston 18. Hereinafter, the # 1 and # 6 cylinders are referred to as a first group, the # 2 and # 5 cylinders are referred to as a second group, and the # 3 and # 4 cylinders are referred to as a third group. The internal combustion engine 10 is configured such that the pistons 18 belonging to the same group move with the same phase, and the pistons 18 belonging to different groups move with a phase difference of 2π / 3 from each other. Has been. Further, the internal combustion engine 10 is configured so that the intake stroke, the compression stroke, the explosion (expansion) stroke, and the exhaust stroke are executed while maintaining a phase difference of 360 ° CA among the cylinders belonging to the same group. ing.

  A crank angle sensor plate 24 (see FIG. 2) is fixed to the crankshaft 22. As shown in FIG. 2, a tooth portion 26 and a missing tooth portion 28 are formed on the outer periphery of the crank angle sensor plate 24. A plurality of teeth 30 are formed on the tooth portion 26 at predetermined intervals. On the other hand, the teeth 30 are not formed in the missing tooth portion 28 over a predetermined length.

  As shown in FIG. 1, a pickup sensor 32 is disposed in the vicinity of the crank angle sensor plate 24 at a position facing the outer peripheral surface thereof. When the crank angle sensor plate 24 rotates, the teeth 30 of the crank angle sensor plate 24 repeatedly approach and separate from the pickup sensor 32. The pickup sensor 32 outputs a pulse signal in accordance with the proximity and separation of the teeth 30. Hereinafter, the crank angle sensor plate 24 and the pickup sensor 32 are collectively referred to as a crank angle sensor 34. The engine ECU 12 detects the rotational speed of the internal combustion engine 10 (hereinafter referred to as engine rotational speed NE) based on the output signal of the crank angle sensor 34.

  When the pickup sensor 32 faces the tooth portion 26, the crank angle sensor 34 outputs one pulse signal every time the crankshaft 22 rotates by 10 ° CA (see FIG. 3B). Hereinafter, this signal is referred to as a crank angle signal. The crank angle sensor 34 outputs a new pulse signal when the crankshaft 22 rotates 30 ° CA after the crank angle signal is output before and after the pickup sensor 32 is opposed to the toothless portion 28. Hereinafter, this signal is referred to as a missing tooth signal. The crank angle sensor 34 has a crank angle of 150 ° (hereinafter, this crank angle is referred to as 150 ° BTDC) before the piston 18 of the # 1 cylinder or the piston 18 of the # 6 cylinder reaches the top dead center (TDC). It is configured to output a missing tooth signal when it arrives.

  A water temperature sensor 36 is disposed on the wall surface of the cylinder block 14. The water temperature sensor 36 outputs an electrical signal corresponding to the temperature of the cooling water flowing inside the water jacket 16. The output signal of the water temperature sensor 36 is supplied to the engine ECU 12. The engine ECU 12 detects the cooling water temperature THW based on the output signal of the water temperature sensor 36.

  A cylinder head 38 is fixed to the upper part of the cylinder block 14. A combustion chamber 40 is formed between the cylinder head 38 and the piston 18. An intake port and an exhaust port communicating with the combustion chamber 40 are formed in the cylinder head 38. The cylinder head 38 also incorporates an intake valve 46 that opens and closes the intake port, an exhaust valve 48 that opens and closes the exhaust port, and a spark plug 50 whose tip is exposed to the combustion chamber 40.

  An igniter 52 is connected to the spark plug 50. An engine ECU 12 is connected to the igniter 52. The engine ECU 12 supplies an ignition signal to the igniter 52 at a timing when ignition is to be performed in any cylinder. The igniter 52 synchronizes with the timing at which the ignition signal is supplied from the engine ECU 12, and in the case where the cylinders belonging to the first group are to be ignited, the ignition plugs 50 of the # 1 and # 6 cylinders and High pressure is applied to the spark plugs 50 provided in the # 2 cylinder and the # 5 cylinder when ignition is to be performed, and the ignition plugs 50 provided to the cylinders # 3 and # 4 when ignition is to be performed for the cylinders belonging to the third group. Supply signal.

  A camshaft 54 for driving the intake valve 46 and a camshaft 56 for driving the exhaust valve 48 are disposed inside the cylinder head 38. The camshafts 54 and 56 are connected to the crankshaft 22 via a timing belt (not shown), and rotate at a rotational speed that is 1/2 that of the crankshaft 22. Cams 54 and 56 are formed with cams for opening and closing the intake valve 46 and the exhaust valve 48 of each cylinder at an appropriate timing. The intake valve 46 and the exhaust valve 48 of each cylinder perform an opening / closing operation once every time the camshafts 54 and 56 make one rotation, that is, every time the crank angle of the internal combustion engine 10 changes by 720 °.

  A cam position sensor 60 is disposed on the camshaft 56 that drives the exhaust valve 48. The cam position sensor 60 outputs one pulse signal while the camshaft 56 makes one rotation. An output signal from the cam position sensor 60 is supplied to the engine ECU 12. The engine ECU 12 detects the crank angle of the internal combustion engine 10 based on the output signal of the cam position sensor 60 and the output signal of the crank angle sensor 34.

  An intake manifold 64 communicates with the intake port of the internal combustion engine 10. An injector 66 is disposed in the intake manifold 64. Fuel is supplied to the injector 66 via a fuel pipe (not shown). The injector 66 is opened only during a period when a drive signal is supplied from the engine ECU 12 and injects fuel into the intake port 64.

  The intake manifold 64 communicates with the intake pipe 70. A throttle valve 72 that operates in conjunction with an accelerator pedal is disposed inside the intake pipe 70. In the vicinity of the throttle valve 72, a throttle sensor 74 that outputs an electrical signal corresponding to the opening of the throttle valve 72 is disposed.

  The intake pipe 70 is provided with an air flow meter 76. The air flow meter 76 passes through the air filter 79 and outputs an electrical signal corresponding to the mass weight of the air flowing through the air filter 79. The illustrated air flow meter 76 is a hot wire type air flow meter and incorporates an intake air temperature sensor 69 that detects the temperature of the air flowing through the intake pipe 70. An output signal of the intake air temperature sensor 69 is supplied to the engine ECU 12. Based on the output signal of the intake air temperature sensor 69, the engine ECU 12 detects the temperature of the air taken into the internal combustion engine 10, that is, the intake air temperature THA.

  An exhaust manifold 78 communicates with the exhaust port of the internal combustion engine 10. An O2 sensor 77 is disposed on the exhaust manifold 78. The O2 sensor 77 outputs an electrical signal corresponding to the oxygen concentration in the exhaust gas flowing through the exhaust manifold 78.

  The engine ECU 12 is connected to a starter 80 that realizes cranking start of the internal combustion engine 10. For example, when an ON signal is input from a start switch 88 set in the passenger compartment and operable by the user, the engine ECU 12 sends a signal to the starter relay 84 to drive the starter motor 86. The present invention is not particularly limited to such a configuration of the starter 80. For example, the present invention can be applied to a starter that is activated by a user turning an ignition key instead of the start switch 88. .

  As described above, the engine ECU 12 detects the crank angle of the internal combustion engine 10 based on the output signal of the cam position sensor 60 and the output signal of the crank angle sensor 34. Further, the engine ECU 12 controls the timing for injecting fuel to the # 1 cylinder to the # 6 cylinder based on the crank angle of the internal combustion engine 10.

  3A and 3B show changes in the output signal of the cam position sensor 60 and changes in the output signal of the crank angle sensor 34, respectively. The engine ECU 12 divides the crank angle signal output from the crank angle sensor 34 every time the crank angle changes by 10 °, and a signal generated every time the crank angle changes by 30 °, similarly to the missing tooth signal. Is generated. Hereinafter, this signal and the missing tooth signal are collectively referred to as a 30 ° CA signal. In this embodiment, control of the fuel injection timing of the internal combustion engine 10 is executed based on this 30 ° CA signal.

  As described above, the crank angle sensor 34 outputs a missing tooth signal when the crank angle reaches 150 ° BTDC. Therefore, the engine ECU 12 can determine that the crank angle has reached 150 ° BTDC when the missing tooth signal is supplied from the crank angle sensor 34. Then, after detecting the missing tooth signal, the engine ECU 12 causes the pistons 18 of the # 1 and # 6 cylinders to reach the top dead center TDC when the five 30 ° CA signals are detected. It can be determined that the angle has been reached.

  In the following description, the 30 ° CA signal (that is, the missing tooth signal) detected when the crank angle reaches 150 ° BTDC, and the pistons 18 of the # 1 and # 6 cylinders reach TDC. The 30 ° CA signal detected at this time is referred to as “150 ° BTDC signal” and “360 ° CA signal”, respectively, as shown in FIG.

  As described above, the cam position sensor 60 outputs a pulse signal once every time the crank angle changes by 720 °. Hereinafter, this signal is referred to as a “720 ° CA signal”. In this embodiment, the cam position sensor 60 outputs the pulse signal in synchronism with the time when the 360 ° CA signal is output, as shown in FIGS. 3 (A) and 3 (B).

  The internal combustion engine 10 receives the cam position sensor when the # 1 cylinder piston 18 reaches the TDC while executing the compression stroke, that is, when the # 6 cylinder piston 18 reaches the TDC while starting the intake stroke. 60 is configured to output a “720 ° CA signal”. Therefore, in the internal combustion engine 10, when the 360 ° CA signal and the 720 ° CA signal are detected almost simultaneously, the piston 18 of the # 1 cylinder is TDC in the compression stroke (hereinafter, this position is referred to as compression TDC). It is possible to determine that the piston 18 of the # 6 cylinder has reached the TDC in the intake stroke (hereinafter, this position is the intake TDC). Further, in the internal combustion engine 10, when the 360 ° CA signal is detected independently, the piston 18 of the # 1 cylinder has reached the intake TDC, and the piston 18 of the # 6 cylinder has reached the compression TDC. Can be determined.

  In the six cylinders included in the internal combustion engine 10, the same stroke is sequentially executed every time the crank angle changes by 2π / 3 in a predetermined order. Specifically, for example, when the intake stroke is started in the # 1 cylinder, thereafter, every time the crank angle changes by 2π / 3, # 1 → # 5 → # 3 → # 6 → # 2 → # The intake stroke is started in the order of 4 → # 1. Therefore, if it can be detected that the piston 18 of the # 1 cylinder or the piston of the # 6 cylinder is located in the intake TDC, the state of the other cylinders at that time and the change in the crank angle thereafter. Thus, it is possible to accurately grasp how the states of other cylinders change. Therefore, the engine ECU 12 can detect that the piston 18 of the # 1 cylinder or the piston of the # 6 cylinder is located in the intake TDC after cranking of the internal combustion engine 10 is started, that is, the internal combustion engine 10. At the time when the 360 ° CA signal is detected for the first time after the cranking is started, the states of all the cylinders can be grasped.

  Next, a characteristic configuration of the fuel injection control that is executed when the internal combustion engine 10 is started will be described with reference to FIG.

  FIG. 4 is a flowchart showing a flow of main processing at the time of engine start realized by the engine ECU 12 of the present embodiment.

  First, in step 100, when an ON signal is input from the start switch 88, the engine ECU 12 sends a signal to the starter relay 84, whereby the starter motor 86 drives the battery 90 as a power source, and the starter 80 starts. Is done.

  The engine ECU 12 continues to send a signal to the starter relay 84 and maintains the cranking by the starter 80 until a predetermined time elapses or a predetermined condition is satisfied. In this way, when the internal combustion engine 10 receives inertial assistance by cranking and the internal combustion engine 10 reaches a sufficient engine speed α by the fuel injection / ignition control as described above, the engine ECU 12 operates the engine completely. The start (starting success) is determined. In the following, it is assumed that the signal output to the starter relay 84 is stopped within a period until the engine ECU 12 determines that the engine complete operation has started. That is, the cranking period by the starter 80 and the self-starting period by the internal combustion engine 10 after cranking by the starter 80 until the engine ECU 12 determines that the engine is fully started after the start switch 88 is turned on (non-cranking). Ranking period) exists.

  Specifically, if it is determined in step 110 that it is a cranking period, the process proceeds to step 200, and in step 110, it is determined that the cranking period ends and the engine speed NE is less than the predetermined value α. If (step 120), it is determined that it is a non-cranking period, and the process proceeds to step 300.

  In step 200, the engine ECU 12 monitors the rising characteristic of the engine speed NE during the cranking period, and the injected fuel is determined based on the comparison result with the predetermined threshold value Th of the engine speed NE by the preset cranking. Determine if it burned normally.

  FIG. 5 is a graph showing an increase characteristic of the engine speed NE during the cranking period. As shown by the solid line in FIG. 5, when the injected fuel is normally burned, the rate of increase of the engine speed NE is high and increases to the vicinity of the predetermined value α, whereas the injected fuel is normal. When not burning, as indicated by the wavy line in FIG. 5, the rate of increase of the engine speed NE is low and does not increase to the vicinity of the predetermined value α. That is, when the injected fuel is not burned normally, an increase characteristic of the engine speed NE only by cranking by the starter 80 (hereinafter referred to as “non-combustion increase characteristic”) appears, and the injected fuel burns normally. In this case, a characteristic in which an increase in the engine speed NE promoted by fuel combustion is added to the non-combustion increase characteristic appears.

  Here, the situation in which the injected fuel does not burn properly in the cylinder (so-called misfire situation) is typically likely to occur at extremely low temperatures where fuel vaporization is poor or when the fuel is poor. A part of the injected fuel is blown out and discharged in the subsequent exhaust stroke, but the remaining part remains in the cylinder as residual fuel.

  Therefore, in this step 200, in the present embodiment, an appropriate threshold value Th that can distinguish between two rising characteristics as shown in FIG. 5 is set, and the rising rate of the rotational speed measured during the cranking period is predetermined. If it is greater than the threshold value Th, it is determined that the injected fuel has burned normally. If the rate of increase of the engine speed NE is smaller than the predetermined threshold value Th, the injected fuel has not burned normally. Is made. The appropriate predetermined threshold Th may be, for example, the value on the non-combustion rising characteristic curve itself, or may be a point on a curve passing through the middle point between the two characteristics. In the former case, if the rate of increase in the rotational speed measured during the cranking period corresponds to the non-combustion increase characteristic, it may be determined that the injected fuel is not burned normally.

  If it is determined in step 200 that the injected fuel is not normally burned, the process proceeds to step 500 where the engine ECU 12 determines the next fuel injection amount for the cylinder that is not determined to have burned normally as the residual fuel amount. Correct based on Here, the residual fuel amount can be theoretically obtained by subtracting the amount of blown-through fuel discharged through the exhaust stroke from the amount of injected fuel. However, since it is difficult or impossible to measure the amount of blown fuel during actual control, it is desirable to estimate the residual fuel amount based on a map prepared in advance based on the test results and / or simulation results. .

  FIG. 6 is an example of a map for obtaining the residual fuel amount created in relation to the engine speed NE. In this case, as shown in FIG. 6, a map in which the residual fuel amount decreases as the engine speed NE increases may be used. Alternatively, a three-dimensional or higher map may be created by adding parameters other than the engine speed NE (for example, intake air amount considering time delay) as parameters.

  For example, in step 500, the engine ECU 12 sets the next fuel injection amount for the cylinder that is not determined to have been burned normally as the normal fuel injection amount (when it is determined that the fuel has been burned normally). This is derived by subtracting the residual fuel amount obtained as described above from the fuel injection amount for the cylinder). Here, the next time refers not only to the next injection timing for a cylinder for which it is not determined that the fuel has burned normally this time, but also the internal combustion engine 10 stops during the cranking period, and the ON signal is input again from the start switch 88. In the case, the initial injection timing at the time of restart is also included.

  As described above, according to this embodiment, the amount of fuel injected for the next expansion stroke is equal to the estimated residual fuel amount with respect to the cylinder that is not determined to have burned normally in the current expansion stroke. As a result, the amount of fuel sealed in the cylinder in the next expansion stroke becomes a normal value. Therefore, according to the present embodiment, even when the fuel does not burn normally in the expansion stroke, the fuel is not over-rich due to the residual fuel (and its accumulation), and excellent startability is ensured. However, it is possible to prevent the emission from deteriorating.

  It should be noted that in the above step 200, for the cylinder that is determined to have burned normally in the current expansion stroke, the amount of fuel injected for the next expansion stroke is corrected based on the residual fuel amount. It is decided without.

  Returning to FIG. When the starter 80 is stopped and the cranking period ends, the process of step 300 is executed for a period until the engine ECU 12 determines that the engine is fully activated (non-cranking period).

  In step 300, the engine ECU 12 monitors the increase characteristic (and / or the change characteristic of the crank angle) of the engine speed NE during the non-cranking period, and increases the engine speed NE immediately after ignition of the cylinder that injected the fuel. Based on the rate (and / or the change rate of the crank angle), it is determined whether or not the injected fuel has burned normally.

  FIG. 7 is a graph showing an increase characteristic of the engine speed NE during the non-cranking period. As indicated by the solid line in FIG. 5, when the injected fuel is normally burned at each ignition timing (arrow in the figure), the subsequent engine speed NE rises and the crank time until the next ignition is short. On the other hand, when the injected fuel does not burn normally, the fuel burns normally, as shown by the wavy line in FIG. 5 (the wavy line indicates an example in which combustion did not occur at the second ignition timing). There is a tendency that the engine speed NE decreases at a non-ignition timing and the crank time until the next ignition becomes long.

  Therefore, in this embodiment, in this embodiment, in order to distinguish between the two rising characteristics as shown in FIG. 5, for example, when the output interval of the 30 ° CA signal immediately after ignition is shorter than the output interval of the same signal immediately before ignition. In addition, when it is determined that the injected fuel burned normally, and the output interval of the 30 ° CA signal immediately after ignition is longer than the output interval of the same signal immediately before ignition, the injected fuel is not burned normally. Judgment is made. Alternatively, although substantially equivalent, if the sign of the rate of increase of the engine speed NE immediately after ignition is positive, it is determined that the injected fuel has burned normally, and the engine speed NE increases immediately after ignition. When the sign of the rate is negative, it may be determined that the injected fuel is not burning properly.

  In addition, after the cranking of the internal combustion engine 10 is started as described above and the 360 ° CA signal is detected for the first time, the state of all the cylinders can be grasped. It can be determined whether the injected fuel is not burning properly in the cylinder.

  If it is determined in step 300 that the injected fuel is not normally burned, the process proceeds to step 600, where the engine ECU 12 determines the next fuel injection amount for the cylinder that is not determined to have burned normally based on the residual fuel amount. To correct. Here, the residual fuel amount may be estimated and calculated in the same manner as in step 500 described above.

  For example, in step 600, the engine ECU 12 sets the next fuel injection amount for the cylinder that is not determined to have burned normally as the normal fuel injection amount (when the fuel has been burned normally) This is derived by subtracting the residual fuel amount obtained as described above from the fuel injection amount for the cylinder). Here, the next time refers not only to the next injection timing for a cylinder for which it is not determined that the fuel has burned normally this time, but also the internal combustion engine 10 stops during the non-cranking period (so-called engine stall occurs), and the start switch again In the case where the ON signal is input from 88, the initial injection timing at the time of restart is also included.

  As described above, according to this embodiment, the amount of fuel injected for the next expansion stroke is equal to the estimated residual fuel amount with respect to the cylinder that is not determined to have burned normally in the current expansion stroke. As a result, the amount of fuel sealed in the cylinder in the next expansion stroke becomes a normal value. Therefore, according to the present embodiment, even when the fuel does not burn normally in the expansion stroke, the fuel is not over-rich due to the residual fuel (and its accumulation), and excellent startability is ensured. However, it is possible to prevent the emission from deteriorating.

  In step 300, for the cylinder determined to have burned normally in the current expansion stroke, the amount of fuel injected for the next expansion stroke is corrected based on the residual fuel amount. It is decided without.

  Next, a preferred modification / improvement example that may be applied to the process of step 200 of the above-described embodiment will be described.

  In this modification, in step 200 shown in FIG. 4, the predetermined threshold value Th is corrected according to the engine water temperature and / or the voltage of the battery 90 serving as the power source of the starter 80.

  FIG. 8 shows an increase characteristic (non-combustion increase characteristic) of the engine speed NE with only cranking by the starter 80. This non-combustion rise characteristic corresponds to the characteristic indicated by the broken line in FIG.

  As shown in FIG. 8A, the non-combustion rise characteristic changes according to the engine water temperature. That is, when the engine water temperature is low, the viscosity of the lubricating oil is so high that the friction is increased and the rate of increase in the engine speed NE is reduced. Therefore, the engine ECU 12 changes the predetermined threshold Th applied to the rate of increase of the engine speed NE as described above based on the output signal (cooling water temperature THW) of the water temperature sensor 36. Specifically, the predetermined threshold value Th is changed so as to increase as the engine water temperature increases. This compensates for the change in the non-combustion rise characteristic that occurs according to the difference in environmental conditions, and realizes the determination in step 200 and step 300 (determination of whether the injected fuel burned normally) with high accuracy. can do. It should be noted that the determination of whether or not the injected fuel has burned normally may be realized using an ion current sensor or the like as an auxiliary or alternative.

  Similarly, as shown in FIG. 8B, the non-combustion rise characteristic changes according to the voltage of the battery 90 serving as the power source of the starter 80. That is, when the voltage of the battery 90 is low, the driving force by the starter 80 is lowered by that amount, and the rate of increase of the engine speed NE is lowered. Therefore, the engine ECU 12 changes the predetermined threshold Th applied to the rate of increase of the engine speed NE as described above based on the voltage of the battery 90. Specifically, the predetermined threshold value Th is changed so as to increase as the voltage of the battery 90 increases. This compensates for the change in the non-combustion rise characteristic that occurs according to the difference in the state of the battery 90, and makes the determination in step 200 and step 300 (determination of whether the injected fuel burned normally) with high accuracy. Can be realized.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the above-described embodiment, the six-cylinder internal combustion engine 10 has been described as an example, but it is naturally applicable to other types (for example, a four-cylinder internal combustion engine).

  In the above-described embodiment, the change in the crank time before and after ignition is calculated using a 30 ° CA signal generally used in an engine. However, a 10 ° CA signal or a similar signal can also be used. It is.

  In the above description, for convenience of explanation, it is assumed that the signal output to the starter relay 84 is stopped within the interval until the engine ECU 12 determines that the engine is fully activated. Such a premise is not essential, and the cranking period by the starter 80 is continued after the start switch 88 is turned on until the engine ECU 12 determines that the engine is fully operational (so-called cranking hold). Even if it is a structure controlled), it is applicable. In such a configuration, the process of step 200 (step 500) may be executed until it is determined that the engine is fully operational. Further, after it is determined that the engine complete operation has started, the processing in step 300 (and step 600) may be executed.

1 is a system configuration diagram of an embodiment of an internal combustion engine 10 to which a fuel injection control device of the present invention is applied. FIG. 6 is a diagram illustrating an example of a crank angle sensor plate 24. FIGS. 3A and 3B are diagrams showing changes in the output signal of the cam position sensor 60 and changes in the output signal of the crank angle sensor 34, respectively. It is a flowchart which shows the flow of the main processing at the time of engine starting implement | achieved by engine ECU12 of a present Example. It is a graph which shows the increase characteristic of the engine speed NE during a cranking period when the injected fuel burns normally (solid line) and does not burn (broken line). It is an example of the map which defines the characteristic of the amount of residual fuel with respect to engine speed NE. It is a graph which shows the rise characteristic of the engine speed NE during the non-cranking period when the injected fuel burns normally (solid line) and does not burn (broken line). It is a graph which shows the increase characteristic at the time of non-combustion of the engine speed NE which changes according to engine water temperature and battery voltage.

Explanation of symbols

10 Internal combustion engine 12 Electronic control unit (ECU)
22 Crankshaft 34 Crank angle sensor 54, 56 Camshaft 60 Cam position sensor

Claims (12)

Combustion presence / absence determining means for determining whether or not the injected fuel burned normally;
A residual fuel amount estimating means for estimating a residual fuel amount remaining in the cylinder without burning, out of the fuel injection amount injected into the cylinder, with respect to a cylinder in which fuel is not normally determined by the combustion presence / absence determining means;
Fuel injection amount correction means for correcting the next fuel injection amount for the cylinder that is not determined to be normally burned by the combustion presence / absence determination means based on the residual fuel amount estimated by the residual fuel amount estimation means. A fuel injection amount control device. Means for memorizing the amount of fuel injected when starting the internal combustion engine, and measuring the rate of increase of the engine speed NE immediately after ignition of the cylinder that injected the fuel and / or a predetermined crank time;
2. The fuel injection amount control device according to claim 1, wherein the combustion presence / absence determining means determines whether or not the injected fuel is normally burned based on the rate of increase and / or a predetermined crank time.   The residual fuel amount estimation means includes blow-by fuel amount estimation means for estimating the amount of fuel blown out from the cylinder in an exhaust stroke, and estimates the residual fuel amount from the blow-through fuel amount and the fuel injection amount. 3. The fuel injection amount control device according to 2.   The fuel injection amount control device according to claim 1 or 2, wherein the blow-by fuel amount estimation means estimates a blow-by fuel amount that changes according to the engine speed NE.   5. The fuel injection amount control device according to claim 4, wherein the blow-by fuel amount estimation means estimates the blow-by fuel amount based on a predetermined map using at least the engine speed NE as a parameter.   When the cranking by the starter is performed, the combustion presence / absence determining means determines that the fuel consumption is higher when the measured increase rate of the engine speed NE is higher than a predetermined reference compared to a predetermined threshold value of the engine speed NE by cranking set in advance. The fuel injection amount control device according to claim 1, wherein it is determined that the fuel has burned normally.   After the cranking by the starter, the combustion presence / absence determining means compares a predetermined crank time immediately before ignition with the crank time immediately after ignition, and if the crank time immediately after ignition is shorter, the fuel burns normally. The fuel injection amount control device according to claim 1, wherein the fuel injection amount control device determines that the fuel injection has occurred.   The fuel injection amount control device according to claim 6, wherein the predetermined threshold value corresponds to an increase rate of the engine speed NE that is only cranked by a starter.   The fuel injection amount control device according to claim 6, wherein the predetermined threshold value is corrected according to an engine water temperature and / or a state of a battery serving as a power source of the starter.   A computer-readable program for causing a computer to function as the fuel injection amount control device according to any one of claims 1 to 9.   The computer-readable recording medium which recorded the program of Claim 10. Determining whether the injected fuel burned normally;
Estimating a residual fuel amount remaining in the cylinder without burning among the fuel injection amount injected into the cylinder for a cylinder that is not determined to be normally burned by the combustion presence / absence determining means;
Correcting the next fuel injection amount for the cylinder, which is not determined to be normally burned by the combustion presence / absence determining means, based on the residual fuel amount estimated by the residual fuel amount estimating means. Fuel injection amount control method.

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